SPREAD-SPECTRUM FREQUENCY MODULATED OSCILLATOR CIRCUIT, FREQUENCY MODULATED OSCILLATOR CIRCUIT AND ELECTROMAGNETIC INTERFERENCE REDUCTION METHOD

摘要

PPROBLEM TO BE SOLVED: To provide a spread-spectrum frequency modulated oscillator circuit available as a clock. PSOLUTION: The spread-spectrum frequency modulated oscillator circuit includes reference elements, such as a resistor, a voltage controlled oscillator, and a first circuit coupled to the reference element and the voltage-controlled oscillator and configured to supply a first control signal to the oscillator and to oscillate the oscillator at a frequency, corresponding to a value of the reference element. A second circuit configured to supply a random signal to the oscillator dithers the frequency of the oscillator. In order to generate in the oscillator random frequency modulation which is as accelerated as reducing EMI, but is not so accelerated to the extent that a controlled device such as a switch regulator cannot trace it, the oscillator includes a third circuit configured to control the change rate of the oscillator frequency and sets the change rate to the fixed rate of the oscillator frequency (1) and to control the frequency change amount of the oscillator frequency and to set the frequency change amount to the fixed rate of the oscillator frequency (2). PCOPYRIGHT: (C)2007,JPO&INPIT